Conventional drawing techniques using pressurized steam have been known in the fiber manufacturing industry. When pressurized steam is used, a higher temperature is obtained than when using hot water under atmospheric conditions, and the presence of water leads to a plasticizing effect on the cellulose polymer, thus resulting in drawing at a high stretch ratio.
On the other hand, when a pressurized steam drawing apparatus is used, pressurized steam may cause the fiber yarn to sway, and the yarn may touch structural members in the apparatus. Especially in the labyrinth seal section of the steam drawing apparatus, in order to improve the sealing effects of steam, it is preferred to employ a labyrinth seal structure having multiple plate pieces extending at right angles from the inner-wall surface of the seal chamber toward the yarn. However, when the yarn touches the labyrinth seal section, such contact may cause problems such as damaged yarn surface, broken single fibers, formation of fuzz, or entirely cut yarn. Such problems may cause further fuzz during flameproofing and carbonization process and may lower the quality of a subsequently obtained carbon fiber.
As for preventing fuzz when drawing yarn using an apparatus with pressurized steam, methods such as follows have been proposed, for example: a method for squeezing yarn immediately before steam is applied to the yarn as described in Japanese Patent Laid-Open Publication H7-70862 (patent publication 1); a method for providing a steam box to preheat the introduced yarn as described in Japanese Patent Laid-Open Publication H8-246284 (patent publication 2); a method for removing the twist of the yarn by positioning a cylindrical guide immediately before the drawing apparatus and by bringing the yarn into contact with the guide as described in Japanese Patent Laid-Open Publication 2008-240203 (patent publication 3), Japanese Patent Laid-Open Publication 2009-174073 (patent publication 4) and the like.